Communication cable



Sept. 8, 1936. E. FISCHER COMMUNICATION CABLE Filed June 50, 1932 Fla. 1.

NON- H Y6 Rosco P/C RUBBER y MA TERI/1L 0/? CELL ULOSE DERIVATIVE Patented Sept. 8, 1936 UNITED STATES PATENT OFFICE COMMUNICATION CABLE ration of Germany Application June 30, 1932, Serial No. 620,088 In Germany May 30, 1931 12 Claims. (Cl. 173-265) My invention relates to communication cables, and more particularly to communication cables with air-space conductors.

To reduce the capacity of communication cables it has hitherto been customary to construct, as a rule, the conductors of cables for communication purposes as paper-insulated air-space conductors. The construction of such conductors has been carried out in most cases by spirally winding around each metallic conductor a single or multiple cord made of fibrous material and placing over this cord an envelope consisting of the same material, especially of paper. The cables made up of such paper-insulated air-space conductors must as is well known be subjected, owing to the water contained in the fibrous materials, to a thorough and careful drying at high temperatures (above 100 C.) so as to attain favorable electrical values. Apart from the fact that this drying process requires a considerable amount of time, the mechanical properties of the fibrous material are thereby aiiected unfavorably. This is particularly the case if the drying is carried out to a great extent in order to minimize the dielectric losses. A further disadvantage of the paper-insulated air-space conductor lies in the fact that when installing communication cables particular care should be taken to prevent the fibrous material from reabsorbing moisture. My invention contemplates a communication cable with air-space conductors in the construction of which instead of the hitherto known strongly hygroscopic materials, materials are employed which are not or only to a relatively slight extent hygroscopic and which have smaller dielectric losses than paper athigh frequencies. Such materials are, for instance, cellulose ester, cellulose ether, tjipetir and rubbers having small dielectric losses, particularly rubber treated with suitable swelling media. The material known in the art and in commerce under the name tjipetir, aforementioned, constitutes a resinfree or only very slightly resinous rubber or gutta percha-like product grown on a Dutch rubber plantation in Java, from which plantation it derives its name. In its commercial qualities it is almost white, probably due to the refining processes to which it is subjected. Electrically it has 50 great dielectric strength, its dielectric constant having a value of about 2.6, its loss angle being smaller than 2 l0- These materials may be used as spacers instead of the usual paper cord. It is, however, also pos- 55 sible to employ as spacers a suitable predried paper cord and to use for the outer envelope of the conductors the above practically non-hygroscopic materials. In the majority of cases it is of advantage to use as material both for the spacer and the outer envelope the above said materials having small dielectric losses. In this way, a further marked advantage is attained in that a drying in the ordinary sense such as is the case with paper-insulated air-space conductors may be dispensed with. But even the replacing, for instance, of only the hitherto customary paper cords or of only the outer envelope by one of the above said practically non-hygro scopic materialswould prove advantageous, since owing to the small dielectric losses of said materials as compared with pure paper-insulated airspace conductors, a slighter attenuation is attained, which is of great importance, particularly for high frequencies.

If materials of relatively high elasticity, for instance, rubber or rubber mixtures are according to the invention employed in the construction of air-space conductors it may be preferable, in or-' der to increase the strength thereof, to insert in the same, materials of great strength; for instance rayon threads or the like. The outer en velope may consist of one or more layers of ribbon, wrapped spirally upon each conductor. It may, however, also be applied in such a manner that one or more ribbons consisting of the above said practically non-hygroscopic materials are plaited around the entire length of the conductor and held together by binders. The overlapping joints of the ribbons, if desired, may be glued together so as to result in a closed tube as outer envelope.

In the accompanying drawings an embodiment of my invention is illustrated by way of example.

In these drawings Fig. 1 represents an individual cable conductor constructed according to the invention, and Fig. 2 represents a portion of a cable containing a number of such conductors.

Referring to the drawings, I denotes the cable containing a plurality of conductors, 2 denotes an individual copper conductor, 3 the spacer which in this case consists of a rubber mixture having small dielectric losses, 3a a thread material of greater tensile strength than the spacer, for instance rayon, and 4 the outer envelope of ribbons wrapped spirally upon the conductor 2 and consisting of the same rubber mixture.

I claim as my invention:

1. A communication cable composed of a plurality of individually air spaced conductors, each conductor having an individual insulating envelope wound about said conductor and an insulating spacer wound directly onto said conductor for supporting said envelope throughout on said conductor in spaced relation thereto, at least one of said insulating elements consisting at least partly of substantially nn-hygroscopic materials selected from the group consisting of cellulose derivatives and rubbery substances, having smaller dielectric losses than paper at high frequencies.

2. A communication cable composed of a plurality of individually air spaced conductors, each conductor, having an individual insulating envelope wound about said conductor and an insulating spacer wound directly onto said conductor for supporting said envelope throughout on said conductor in spaced relation thereto, at least one of said insulating elements consisting of substantially non-hygroscopic materials selected from the group consisting of cellulose derivatives and rubbery substances, having smaller dielectric losses than paper at high frequencies.

3. A communication cable composed of a plurality of individually air spaced conductors, each conductor having an individual insulating envelope wound about said conductor and an insulating spacer would directly onto said conductor for supporting said envelope throughout on said conductor in spaced relation thereto, at least one of said insulating elements consisting of substantially non-hygroscopic cellulose derivatives having smaller dielectric losses than paper at high frequencies.

4. A communication cable composed of a plurality of individually air spaced conductors, each conductor having an individual insulating envelope and insulating spacers for supporting said envelope in spaced relation on said conductor, at least one of said insulating elements consisting at least partly of a practically non-hygroscopic rubbery substance, having smaller dielectric losses than paper at high frequencies.

5. A communication cable composed of a plurality of individually air spaced conductors, each conductor having an individual insulating envelope and insulating spacers for supporting said envelope in spaced relation on said conductor, at least one of said insulating elements consisting of a practically non-hygroscopic rubbery substance, having smaller dielectric losses than paper at high frequencies.

6. A communication cable composed of a plurality of individually air spaced conductors, each conductor having an individual insulating envelope and insulating spacers for supporting said envelope in spaced relation on said conductor, at least one of said insulating elements consisting of practically non-hygroscopic rubber having smaller dielectric losses than paper at high frequencies.

'7. A communication cable composed of a plurality of individual air spaced conductors, each conductor having an individual insulating en velope and insulating spacers for supporting said envelope in spaced relation upon said conductor, at least one of said insulating elements consisting at least partly of practically non-hygroscopic rubber swelled with suitable swelling means, said rubber having smaller dielectric losses than paper at high frequencies.

8. A communication cable composed of a plurality of individual air spaced conductors, each conductor having an individual insulating envelope and insulating spacers for supporting said envelope in spaced relation upon said conductor, at least one of said insulating elements consisting of a practically non-hygroscopic insulating ma terial having smaller dielectric losses than paper at high frequencies and containing inserts made of a material of greater tensile strength than the insulating material itself.

9. A communicationcable composed of a plurality of individual air spaced conductors, each conductor having an individual insulating envelope and insulating spacers for supporting said envelope in spaced relation upon said conductor, at least one of said insulating elements consisting of a practically non-hygroscopic insulating material having smaller dielectric losses than paper at high frequencies and containing inserts made of rayon.

10. A communication cable with air-space conductors, the insulation of said air-space conductors consisting of practically non-hygroscopic tjipetir,- said tjipetlr having smaller dielectric losses than paper at high frequencies.

11. A communication cable with air-space conductors, the insulation of said air-space conductors and the spacers provided for the insulation consisting of practically non-hygroscopic tjipetir, said tjipetir having smaller dielectric losses than paper at high frequencies.

12. A communication cable with air-space conductors, the spacers provided for the insulation consisting of practically non-hygroscopic tjipetir, said tjipetir having smaller dielectric losses than paper at high frequencies.

ERNST FISCHER. 

